The present invention relates to apparatus for perforating webs of paper or other wrapping material which can be utilized in the manufacture of filter plugs, plain or filter tipped cigarettes, cigars, cigarillos and analogous rod-shaped articles which constitute or form part of smokers' products. More particularly, the invention relates to improvements in apparatus wherein a running web of cigarette paper or other wrapping material of cigarettes, filter plugs and/or the like is perforated by electric sparks which are discharged across the gaps between pairs of electrodes installed adjacent to the path of movement of the web and connected to a source of high-voltage impulses.
In the manufacture of so-called light cigarettes, the wrapper of the cigarette is formed with holes or perforations which admit cool atmospheric air into the column of tobacco smoke. The thus admitted air influences the nicotine- and/or the condensate-content of the smoke; therefore, such holes are indispensable in many brands of presently popular rod-shaped smokers' products. The holes can be made in the wrapper of the tobacco filler and/or in the uniting band which connects the tobacco filler with a simple or complex filter plug.
U.S. Pat. No. 3,475,591 granted on Oct. 28, 1969 to Fujii et al. discloses an apparatus which comprises a row of electrodes at one side of a running cigarette paper web. The electrodes are connected in parallel and are further connected with a source of high-voltage impulses. A single counterelectrode is installed at the other side of the path of movement of the web. When the electrodes receive an impulse, a spark discharge takes place between the electrodes and the counterelectrode whereby the electric sparks perforate the adjacent portions of the running web. Such apparatus exhibit the drawback that the holes are relatively small and that the cross-sectional areas of the holes are not uniform. Therefore, the rate at which atmospheric air is admitted into and is mixed with the column of tobacco smoke is likely to vary from cigarette to cigarette.